Isolated Sigma-Delta Modulator
Preliminary Technical Data
AD7401A
FEATURES
GENERAꢀ DESCRIPTION
20 MHz maximum external clock rate
Second-order modulator
16 bits no missing codes
2 ꢀSB INꢀ typical at 16 bits
3.5 µV/°C maximum offset drift
On-board digital isolator
The AD7401A1 is a second-order, Σ-Δ modulator that converts
an analog input signal into a high speed, 1-bit data stream with
on-chip digital isolation based on Analog Devices, Inc.
iCoupler® technology. The AD7401A operates from a 5 V power
supply and accepts a differential input signal of ±±00 mV
(±ꢀ±0 mV full scale). The analog input is continuously sampled
by the analog modulator, eliminating the need for external
sample-and-hold circuitry. The input information is contained
in the output stream as a density of ones with a data rate up to
±0 MHz. The original information can be reconstructed with an
appropriate digital filter. The serial I/O can use a 5 V or a ꢀ V
supply (VDD±).
On-board reference
ꢀow power operation: 20 mA maximum at 5.25 V
−40°C to +125°C operating range
16-lead SOIC package
AD7400A, internal clock version
Safety and regulatory approvals
Uꢀ recognition
3750 V rms for 1 minute per Uꢀ 1577
CSA Component Acceptance Notice #5A
VDE Certificate of Conformity
DIN EN 60747-5-2 (VDE 0884 Part 2): 2003-01
DIN EN 60950 (VDE 0805): 2001-12; EN 60950: 2000
The serial interface is digitally isolated. High speed CMOS,
combined with monolithic air core transformer technology,
means the on-chip isolation provides outstanding performance
characteristics, superior to alternatives such as optocoupler
devices. The part contains an on-chip reference. The AD7401A
is offered in a 16-lead SOIC and has an operating temperature
range of −40°C to +1±5°C.
VIORM = 891 V peak
1 Protected by U.S. Patents 5,952,849; 6,873,065; and 7,075,329. Other patents
pending.
APPꢀICATIONS
AC motor controls
Data acquisition systems
A/D + opto-isolator replacements
FUNCTIONAꢀ BꢀOCK DIAGRAM
V
V
DD2
DD1
AD7401
V
V
+
IN
T/H
Σ-∆ ADC
–
IN
UPDATE
WATCHDOG
ENCODE
DECODE
BUF
MDAT
REF
CONTROL LOGIC
WATCHDOG
UPDATE
DECODE
MCLKIN
ENCODE
GND
GND
1
2
Figure 1.
Rev. PrA
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